Effects of microvaristor material on the occurrence of partial discharges upon insulators in rain test

Finite element method (FEM) simulations of high voltage composite insulators including nonlinear field grading materials in rain test are presented. These silicone polymer materials are filled with ZnO microvaristors, which feature semi-conductive field-dependent material properties. The effects of adding layers to a composite insulator made of semi-conductive ZnO microvaristor material on the voltage resistance is analyzed using numerical simulations. The resulting homogenization of the electric field is compared for various ZnO layer setups in rain test.